Dynamo electric machine



Feb. 9, 1932. R. H. SULLIVAN 1,844,721

DYNAMO ELECTRIC MACHINE Filed March 27, 1928 Hmwemitmw Patented Feb. 9, 1932 UNITED STATES .PATENT OFFICE RAYMOND H. SULLIVAN, OF ROCHESTER, NEW YORK, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO NORTH EAST APPLIANCE CORPORATION, OF ROCHESTER, NEW YORK, A

CORPORATION OF NEW YORK DYNAMO ELECTRIC MACHINE Application filed March 27, 1928. Serial No. 265,186.

This application is, in part, a continuation of my application relating to dynamo electric machines, tiled May 16, 1927, Serial N 0. 191,803.

This invention relates to electric generators of the 3-brush type, in which the shunt field-winding is connected across one or more of the main brushes and one or more auxiliary or regulating brushes, in order to regulate the output of the machine by the effect of field distortion.

In machines of the 3-brush type it has been customary to mount the regulating brush or brushes with provision for adjusting the angular distance between them and the main brushes, such adjustment being used to vary the maximum output of the machine under given conditions. At the same time the main brushes have been mounted either in fixed position, or with provision for slight adjustment to permit them to be set on the neutral position for some predetermined condition of speed and load. This arrangement involves certain complications in manufacture, and the adjustment of the main brushes, where provided, is not commonly or conveniently used except to give these brushes a permanent predetermined setting as an incident of assembling in the factory.

One object of the present invention is to construct machines of the type in question in such a way that, by a single convenient operation, the output may be changed and, at the same time, the setting of the main brushes may be corrected in accordance with the changed output. Another object is to produce a 3-brush machine in which, as an incident of manufacture or repair, all of the brushes may be assembled, with their mounting, as a simple and inexpensive separate unit, and in which the expense and complication of independent adjusting means for the main brushes and the regulating brushes may be avoided.

To the foregoing ends it is proposed to mount all of the brushes on a single angularly adjustable support, and to provide means readily accessible at the outside of a machine for adjusting the support, the relation of the several brushes on the support being such that adjustment for output results in desirable changes in the setting of the main brushes.

In the accompanying drawings, Fig. 1 is a vertical sectional view of the end of a generator, showing brushes and a brush mounting arranged in accordance with the present invention, and Fig. 2 is a detail sectional view on the line 22 in Fig. 1. Fig. 3 is a diagram of the machine.

In Fig. 1 the invention is illustrated as embodied in a four pole generator having two main brushes 5 and 6, located apart, approximately at two opposite neutral points of the commutator, and a third or regulating brush 7 located intermediate the other two neutral points. These brushes are shown as arranged to slide in guides 8, which are mounted on an annular plate or support 9, seated against a shouldered bearing 20 on the head 11 of the generator. The support is centered and held in place by three studs 10, which engage slots 12 in the support. The brush guides are all fixed in permanent relative angular position upon the support, since no relative adjustment is either necessary or desirable. At one point the support is provided with a series of gear-teeth 13, engaged by a pinion 14 which constitutes the means for adjusting the brushes. The pinion is mounted on the inner ends of a stem which is journalled in an opening in the head 11, as shown in Fig. 2, and this stem has a slotted head 19 accessible at the outside of the machine, so that the pinion may be turned conveniently by means of a screw driver. By rotatin the pinion the support, and the parts carried thereby, may be turned through a substantial angle in either direction about the axis of the machine.

It will be understood that the several brush guides are insulated from each other, either by making the support 9 of insulating material or in any other convenient manner. The details of form and construction of the brushes, the brush guides and the supporting and adjusting means are not essential to the invention, the only requirement being that the brushes be so assembled with their guiding and supporting means that they are si- Hit) multaneously adjustable, by a single operation, through equal angles in the same direction. 7

In Fig. 3 the machine is shown, for simo plicity, as a two-pole'machine, the main brushes 5 and 6 being connected with the load circuit through main conductors 16, and the shunt field winding 15 being connected between the main brush 5 and the regulating brush 7. If the armature rotates clockwise, as indicated by the arrow, an increase in the maximum output of the machine may be secured by moving the regulating brush 7 clockwise, and, with the machine constructed as described, such movement results in equal similar movements of the main brushes, so

that all of the brushes take up a new position such, for example as that indicated by the lines 17. In the diagram, the brushes are shown as in an intermediate position suitable for a medium output, the main brushes in this position being on the neutral position. It a minimum output is desired, the brushes may be adjusted to positions such as those indicated by the lines 18.

While the adjusting movement of the main brushes in the same direction as the third brush is desirable, as before described, the extent of such adjustment of the main brushes should theoretically be less than that of the third brush. Practically, however, the exact position of the main brushes is not important when the machine is adjusted for the lower outputs. iVhen' operating with small output there is little tendency to commutating diflicultics. and it is not important that the machine have the lowest possible cut-in point, that is, that it reach the required minimum voltage at'the lowest possible speed.

Accordingly, a practical compromise is secured by so arranging the brushes on their support that the main brushes will be approximately on the no-load neutral points when the regulating brush is at a position intermediate between those for minimum and maximum output. In such an arrangement, the machine will have the minimum cut-in speed whenadjusted for such medium output, this being the combination of concitions most usually desirable in such machines. hen the brushes are adjusted for high or maximum output the position of the main brushes will then be corrected in the required direction, and approximately the required amount, to minimize the tendency towards gular relation, said support being carried by said frame and angularly movable about the no-load neutral position of the generator,

with means accessible at the outside of the generator for moving all of said brushes simultaneously so as to increase the output of the third brush generator as the brushes are moved in the required direction of the neutral position and vice versa.

'2. In a third'brush generator having main brushes and a regulating brush, the field windings being connected to the regulating brush and one of said main brushes, the combination of a frame, a unitary support upon which all of said brushes are mounted in permanent angular relation, said support being adj ustably carried by said frame, with means accessible from the outside of the frame for adjusting said support whereby the field excitation may be increased so as to increase the output of the generator and vice versa. Z I

3. In a third brush generat r. the combina tion, with main brushes and a regulating brush, of a brush mounting comprising a single support upon which all of said brushes are mounted in permanent angular relation, and means accessible at the outside of the generator for rotating said support about the axis of the generator so that the main brushes are moved relative to their no-load neutral position.

RAYMOND H. SULLIVAN.

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